Optical couplers, such as mode couplers, are used extensively in integrated optics to split and to combine light signals propagating through an optical waveguide structure. Since an optical coupler splits an input into several outputs, each output will have less optical power than a corresponding input. This power drop is loosely termed as splitting loss. For example, a 1×2, 50-50 coupler has a 3-dB splitting loss beside other losses. This power drop or splitting loss fundamentally limits several useful system and device architectures that otherwise find many applications in electronic systems. For example, data bus architecture, which is ubiquitous in electronic computers and data networks, finds limited applications in optical systems mainly due to splitting losses. Filter designs based on finite or infinite impulse responses (FIR or IIR) also require a series of the splitting of an input signal. The applications in optics of such devices therefore are also limited due to splitting losses.
Current solutions for the splitting losses in conventional optical couplers include passive optical couplers having amplifiers at the inputs and/or the outputs to provide amplification for optical signals being split. However, the splitting and amplification of such optical couplers occur at different locations of the optical coupler and the transition between the active amplification process and the passive splitting require intricate and expensive manufacturing processes. In addition such optical couplers require a plurality of optical amplifiers and may comprise a relatively large form factor.